PS1 / IPP Time Errors

MJD-OBS (a TAI value in smf files) did not have the 2012.07.01 leap second in files for exposures after 2012.07.01 and processed between 2012.07.01 and 2012.11.09. SHUTOUTC is OK.

Between 2015.04.26,16:45 HST and ~2015.05.12,12:00 HST the clocks on the camera readout computers drifted out of NTP lock, accumulating ~113s before the problem was fixed. A table of corrections for the affected images was produced by Craig Rae by using information from one camera computers which did not drift.

From 2015.07.01 to 2015.08.11, some IPP machines received a corrupted version of /etc/localtime, which resulted in incorrect values for SHUTOUTC for data processed on those machines. The smf primary header depends on the XY01 chip, so a fraction of the smfs in this period have the wrong SHUTOUTC values.